1. Debugging statements inserted into a program that emit output or
log indicators of the program's {state} to a file so you can see
where it dies or pin down the cause of surprising behavior. The term
is probably a reference to the Hansel and Gretel story from the
Brothers Grimm or the older French folktale of Thumbelina; in several
variants of these, a character leaves a trail of bread crumbs so as
not to get lost in the woods.
2. In user-interface design, any feature that allows some tracking of
where you've been, like coloring visited links purple rather than
blue in Netscape (also called footprinting).
[glossary]